Backup multiple keyShares for a waaS wallet to Google Drive

Example response

{
  "keyShares": [
    {
      "id": "95b11417-f18f-457f-8804-68e361f9164f",
      "externalKeyShareId": "95b11417-f18f-457f-8804-68e361f9164f"
    }
  ]
}